The invention relates generally to surface mounted connectors on printed circuit boards, and more specifically, to a contact for surface mounted connectors.
The ongoing trend toward smaller, lighter, and higher performance electrical components and higher density electrical circuits has led to the development of surface mount technology in the design of printed circuit boards. As is well understood in the art, surface mountable packaging allows for the connection of the package to pads on the surface of the circuit board rather than by contacts or pins soldered in plated holes going through the circuit board. Surface mount technology allows for an increased component density on a circuit board, thereby saving space on the circuit board.
The ball grid array (BGA) and land grid array (LGA) are two types of surface mount packages that have developed in response to the demand created by higher density electrical circuits for increased density of electrical connections on the circuit board. The ball grid array includes an array of connections on the bottom side of the connector package. In the ball grid array, pins extending into the circuit board are replaced by small solder balls placed on the bottom side of the connector at each contact location. The circuit board, rather than holes, has an array of contact pads matching the solder ball placements on the connector bottom. Connections are made by reflow soldering the solder balls to mechanically and electrically engage the connector to the circuit board. The land grid array is similar to the ball grid array except that, rather than the application of solder balls, the land grid array socket applies sufficient normal force on the package to mate the package on flexible contact beams in the connector.
BGA and LGA technology offer the advantages of higher connection densities on the circuit board and higher manufacturing yields which lower product cost. However, they are not without disadvantages. In particular, during the development of chips, chip sockets, multi-chip modules (MCM's), and other electronic packages using BGA technology, testing of product revisions requires soldering and unsoldering of the packages which, in the case of ball grid array devices, is particularly difficult.
In a prior art electrical interconnect system as disclosed in U.S. Pat. No. 7,070,420, an array of electrical contacts is held in a substrate. Each contact includes a nonconductive elastomeric element and an associated conductive element. The nonconductive element has opposite ends disposed beyond respective opposite sides of the substrate. The conductive element includes a body having opposite ends disposed exteriorly of respective opposite ends of the nonconductive elastomeric element. The opposite ends of the nonconductive elastomeric element resiliently press against the respective opposite ends of the conductive element when a force is applied to the electrical contact.
However, a need remains for a compressible contact system having smaller compressive contacts that can be more easily and economically molded. Further, the contact system should provide a sufficient working range and sufficient compressibility to allow multiple matings and unmatings of electronic packages without soldering and unsoldering of contact connections.